[pianotech] Finish on finish

[Paul McCloud]

Hi, Doug:
    I'd love to learn more about your french polishing technique.  I've tried doing this with Mohawk products, but always ended up with ugly streaks.  They have a product called an amalgamator, which supposedly does what you are doing- filling in alligatored/checked/whatevered old finishes, but  I've not had any luck with it at all.  I do all kinds of touchup on finishes, but never got into the strip and refinish routine.  Sure would be nice if you had a video up on You Tube or something to look at and see how you do it.  Where do you get your Konig products from?
    Paul McCloud
    San Diego


----- Original Message ----- 
From: Douglas Gregg 
To: pianotech at ptg.org
Sent: 11/07/2010 7:20:05 AM 
Subject: Re: [pianotech] Finish on finish


Hi,
 I routinely freshen up finishes on old pianos by using French polishing technique. Specifically, I use Konig brand French polish. If a piano is lightly crazed (ground glass appearance) it can be French polished to a high gloss with no other treatment. If it is deeper as with an orange peel finish, I sand it with 400 grit wet or dry paper with a thin mineral oil lubricant. Then I clean off the oil with some mineral spirits and French polish it. It does not have to be perfectly smooth before French polishing.  It takes two or three polishing sessions for deeply crazed pianos. Give it several days between sessions for the shellac to completely dry. It will show some of the crazing when the first session drys but that will fill in after the second or third session. The beauty of French polish is that it is rubbed on with a pad that only fills depressions without adding finish to the high spots. This levels the finish very effectively.

 I have followed these pianos for years and have found it to be very effective. The other nice feature is that it can be refreshed easily with the same polishing method if there are new scratches or other damage. I almost never strip a piano in my shop. This strips out all the original factory effort to fill the grain and even out  the color. 
The only defect that is hard to French polish out, is fine alligator cracking of finish that goes through the full thickness of the finish. This defect is more commonly seen in a piano that has been resprayed with lacquer over an old finish. I think it is due to differential shrinkage of the less than compatible finishes. It will finally lead, in the worst cases, to large flakes of the finish coming off. There is not much that can be done with such a finish except to attempt to stabilize the flaking with a tung oil varnish such as Formby's tung oil. Otherwise, it has to be stripped. 

I teach French polishing to the local guild members and others in my area. It is nearly a lost art with tremendous effectiveness and great earning power.  Customers often ask me to French polish their antiques after they see what it can do on their piano. 

Douglas Gregg
Classic Piano Doc
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